1. Technical Field
This invention relates to ultraviolet radiation sensors. More particularly, the invention relates to sensors that indicate the level of exposure to ultraviolet radiation.
2. Description of the Prior Art
Exposure to ultraviolet radiation can cause a wide range of deleterious effects in human skin, including dehydration, burning, premature aging, and discoloration. In addition, it has been widely accepted and documented that excessive exposure to ultraviolet radiation can be carcinogenic in humans. Exposure to ultraviolet radiation is of particular concern for individuals who spend a significant amount of time exposed to the sun, and for those who are of fair complexion and are less tolerant to the sun""s ultraviolet rays. In addition, damage to the earth""s ozone layer and its ability to filter out ultraviolet radiation has further raised concern over the harmful effects that exposure to ultraviolet radiation may have.
For the above reasons, a variety of different devices and skin preparations have been developed to limit exposure to solar radiation. So called sunscreen clothing has been developed that filters or blocks ultraviolet radiation. In addition, significant advances have been made in the development and commercialization of topical sunscreen preparations that may be applied to the skin to provide protection from ultraviolet rays
Several such prior art sensors use ultraviolet sensitive inks that change color with increased exposure to ultraviolet rays. The problem with such sensors is that they are purely visual. Many users wear the sensors while engaging in strenuous or fast-paced activities, where little attention is given to the sensor. Thus, a change in color of the sensor often goes unnoticed.
Furthermore, such sensors typically exhibit a gradual change in color as exposure to ultraviolet light is increased. It may therefore be unclear to the user exactly what shade of color corresponds to an unacceptably high level of exposure.
Finally, most ultraviolet radiation sensors are calibrated to indicate the amount of radiation absorbed by untreated skin. If suntan lotion is applied to the skin, the masking effects of the lotion are not reflected in the exposure indicated by the sensor.
What is needed is an ultraviolet radiation sensor that produces not only visual cues indicating excessive exposure, but audible and tactile signals as well. The sensor should also provide a discrete, unambiguous indication of excessive exposure. Lastly, the exposure measured by the sensor should reflect the masking effects of any suntan lotion that may be applied.
An ultraviolet radiation sensor is disclosed that indicates a predetermined cumulative exposure to ultraviolet radiation. The presently preferred sensor comprises a membrane, a base, an ultraviolet degradable adhesive, and an indicating mechanism. The ultraviolet degradable adhesive adheres a portion of the membrane to the base, thereby maintaining the membrane in a biased state. The ultraviolet degradable adhesive fails when a predetermined cumulative exposure has been attained. Upon failure of the adhesive, the membrane reflexively restores itself to an unbiased state and activates the indicating mechanism.
In a preferred embodiment of the invention, the sensor worn by a user to indicate when the skin of the user has been exposed to excessive ultraviolet radiation. In other, equally preferred embodiments of the invention, the membrane produces a sound that is audible to the user when the membrane returns to an unbiased state. The membrane may also produce a tactile sensation that is detectable by the user when the membrane returns to an unbiased state. Additionally, when in an unbiased state, the membrane may possess a tactilely sensible feature for verifying that the membrane has returned to the unbiased state. Various color indicating mechanisms may also be used to advise the user that excessive exposure has been attained.
The sensor may also receive suntan lotion. The extent of lotion absorption and excreation by the membrane are preferably similar to those of the human skin. Thus, the proper degree of ultraviolet exposure is indicated even if suntan lotion is applied by the user.